EVIL, we didn't say you were stupid. Just that from all my learnings from people who have devoted their lives to ancient weaponry, these people have told me that the blood groove doesn't make any difference. If you stab someone, there can't be a suction. Would you like to hear my reasoning behind this? If you shove an object in someones body, air must either escape, or compress. If it can escape, then there is another opening somewhere that would make it so there is no suction. If there is no opening, then the air and organs in the body would simply move out of the way, making a pushing of sorts on the blade. Suction is caused by high pressure on the outside, and low pressure on the inside. Teach me how this low pressure got there, and I will stop argueing.